1. Field of the Invention
The invention relates to a method for removing phosphorus, and more particularly to a method for removing phosphorus with an absorbent.
2. Description of the Related Art
Conventional methods for removing phosphorus from sewage include physicochemical treatment methods, for example, ion-exchange methods and chemical coagulation methods, and biological treatment methods, for example, A2/O method, A/O method, and phoredox method. Physicochemical treatment methods require a large amount of chemical reagents and thereby the cost is very high. Biological treatment methods often produce much sludge which is difficult to handle.
As an ideal technology for removing phosphorus, absorption methods have dual function of removing and recycling phosphorus. The mechanism is that: phosphorus adheres to an absorbent, experiences ion exchange and surface precipitate, and then separates from sewage. The phosphorus can be recycled by desorption.
Absorbent is a key element for absorption method. Conventional absorbents are selected from natural adsorbents, activated alumina or derivatives thereof, or synthetic adsorbents, and so on. However, these absorbents have disadvantages as below:                1) Low absorption capacity, particularly under a low concentration;        2) Low capacity of selective absorption;        3) Low speed of absorption and long reaction time;        4) Difficulty for recycling and instable performance; and        5) The raw material used for preparation of these absorbents is expensive.        